Hydrogen storage properties of two ball-milled composites of Ca(NH 2 ) 2 + 2LiH and CaH 2 + 2LiNH 2 were investigated as a series of searching studies of high performance hydrogen storage materials. About 4.5 mass% hydrogen is desorbed from about 100 • C and the thermal desorption profiles show a peak around 200 and 220 • C for the composites of CaH 2 + 2LiNH 2 and Ca(NH 2 ) 2 + 2LiH, respectively, under a helium flow at 5 • C/min heating rate without any NH 3 emission within our experimental accuracy. The powder X-ray diffraction and infrared absorption spectroscopy indicated that the dehydrogenated states of both composites form "an unknown imide phase" after heating up to 400 • C, while the dehydrogenated states after heating up to 200 • C in vacuum are the mixed phases of Li 2 NH and CaNH. The rehydrogenated state for the ball-milled composite of CaH 2 + 2LiNH 2 is transformed into the composite of Ca(NH 2 ) 2 and 2LiH by repeating the dehydrogenation and rehydrogenation cycles at 180-200 • C.